Helium recovery gas pressure rise in a vertical pipe in a high-rise

[Marcus118]

I have a problem with a helium recovery system that I need help with! Aug 6,2019

We are collecting (recovery) helium from dowers (boil-off) on the 5th floor which boil-off to a recovery piping system.
Its pressure requirements in the piping system needs to be just above atmospheric at the gas connections of the 5th floor dowers
and the gas needs to travel down to the basement (90 ft below) to the the helium bag collection system before running through a compressor for supplying
the purifiers and liquidizers for building reuse.

What I need to know is from the 20,000 cu ft collection bag (max. pressure 1.5 psi above atmospheric) in the basement,
what will be the the pressure rise (90 ft above) in the 5th floor collection piping at the dower connections?

Or since pressure is per pipe diameter area the piping size is not important in the calculation, but its 2"
what is the pressure increase in a 25 foot section of vertical pipe filled with Helium at around atmospheric pressure?

Since the pressure gauges measures the surrounding air pressure as a reference for the piping pressure, is it significant enough to consider
because the dowers are at the same pressure upper elevation?

MRY118

 

[georgeverghese]

Well, you've got the static head of helium gas going up 5 floors, and there is also the friction loss due to helium gas as it travels down the 2inch piping.

Pressure at 5th floor = operating pressure in the collection bag + piping friction drop - static head of helium; all in kpa abs

Static head of helium = rho. g.del(H); where density rho = MW * P/ZRT; Z will depend on the operating temp of the helium gas in this pipe.

For friction drop, refer to your Uni text on flow hydraulics or Crane TP410; add on for additional lengths due to fitting such as elbows and valves. Use the simpler eqn if friction drop is say less than 10kpa, else use the isothermal compressible expression ( if friction drop is >10kpa)